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ConsoleProducer will be updated to accept a new property: null.marker. By default, it will not be set to keep the existing behavior. When set, if any of the fields (, key, value or headers (including individual header values, but not header keys) in the input match the marker, a record with that field set to null will be produced. The

Example:

$ ./bin/kafka-console-producer.sh --bootstrap-server localhost:9092 --topic test --property null.marker=NULL
>NULL               (1)
>NULL more content  (2)

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$ ./bin/kafka-console-producer.sh --bootstrap-server localhost:9092 --topic test --property null.marker=NULL --property parse.key=true --property parse.headers=true
>h0:v0,h1:v1    NULL    myvalue    (1)
>NULL    mykey    NULL             (2)
>h0:,h1:v1    NULL    NULL         (3)
>h0:NULL,h1:v1    mykey    NULL    (4)
>NULL:v0    mykey    myvalue       (5)

1. This will result in a record with key=null, value="myvalue" and headers={"h0": "v0", "h1": "v1"}
2. This will result in a record with key="mykey", value=null and headers=null
3. This will result in a record with key=null, value=null and headers={"h0": "", "h1": "v1"}
4. This will result in a record with key="mykey", value=null and headers={"h0": null, "h1": "v1"}
5. This will result in a record with key="mykey", value="myvalue" and headers={"NULL": "v0"} This is because headers cannot have a null key.

Proposed Changes

This will require small changes in ConsoleProducer/LineMessageReader to accept the new flag and update the generated ProducerRecord accordingly.

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